Thermoplastic fluoropolymers are well known for outstanding combinations of properties including chemical resistance, unique surface characteristics, high service temperatures, and good dielectric characteristics. As a result, fluoropolymer resins are used in a wide variety of applications including wire insulation, cable tubing, film, linings for chemical process equipment, articles for fluid handling in laboratory and manufacturing situations, and the like. The service temperature in some of these applications can be high. As is common for thermoplastics, some properties of fluoropolymers change as temperature increases. Modulus and tensile strength, for example, typically decrease with increasing temperature.
Efforts have been made to improve the physical characteristics of fluoropolymers at elevated temperatures, largely by cross-linking. Approaches to cross-linking usually involve the incorporation of a cross-linking promoter, also called a coagent, such as triallyl cyanurate or triallyl isocyanurate (U.S. Pat. No. 5,353,961) or metallic diacrylate (U.S. Pat. No. 5,409,997) into a fluoropolymer such as ETFE copolymer, followed by treatment with ionizing radiation to effect the cross-linking.
Improved ways to cross-link fluoropolymers and thereby achieve improved properties are desired.